1. Field of the Invention
The present invention relates generally to a method used in processing dipmeter well logs and, more particularly, to new techniques for automatically computing the slope (dip) and direction (azimuth) of subsurface formations. This information is of particular importance in the exploration for natural resources, such as oil and gas.
2. Setting of the Invention
As is well-known in the art, a dipmeter tool is suspended within a wellbore and is passed along the rock face within the wellbore. The dipmeter tool produces signals from several directionally sensitive sensors spaced around movable arms extending from the tool. The signals are processed to allow the log analyst to infer the type of rock around the borehole and the angle and direction of the bedding planes. In particular, most dipmeter tools record variations in electrical conductivity from circumferentially spaced receptors or sensors, the location of the tool in the borehole, and sufficient other information to permit the location of the tool within a geologically meaningful, spatial reference system.
In the prior art, the computer programs required to process the recorded signals from a dipmeter tool were quite specific, i.e., a computer program was written in a manner such that the program could process the signals from only a particular type of dipmeter tool. There is at least one processing system for each tool, and the development and use of a new dipmeter tool required a new processing system. Frequently, these processing systems are incompatible with prior tools, even those made by the same company. Sometimes several different processing systems have been developed to one tool. With many tools, and a multiplicity of processing systems, the answers derived from these systems do not agree with each other, so that there is a need for a dipmeter processing system that is universal in its applicability.
Prior art dipmeter processing systems are generally shown in U.S. Pat. Nos. 4,303,975; 4,320,458; 4,357,660; 4,414,656; and 4,541,275. The most relevant prior art dipmeter processing systems to the present invention are disclosed in U.S. Pat. Nos. 4,348,748 and 4,453,219; however, none of these patents disclosed or suggest a dipmeter processing system that is capable of processing the dipmeter signals from any tool by modeling the particular tool's configuration to be used in dip computation. Other differences between the present invention and the relevant prior art dipmeter processing systems will be mentioned throughout this disclosure below.